The diffusion tensor of lung airways will be measured using hyperpolarized (HP) 3He gas. To date, diffusion tensor measurements in the lung have not been viable due to the very low SNR achieved with protons. It is estimated that the changeover from anisotropy to isotropy in the lung airway structure will be determined. The diffusion tensor will be measured using a technique based on recent work done in fiber mapping of cardiac muscle (E. W. Hsu et al. Magnetic resonance myocardial fiber orientation mapping with direct histological correlation. AJP Heart and Circulatory Physiology 274, 1627-34 (1998)). A number of images will be taken at different gradient values (b-values) and in 6 different gradient combinations.